Physical Layer

Question 0

Bit patterns

Answer 0

Signals designating start and end of frame

Question 1

Three fundamental functions

Answer 1

Data encoding: converting stream of bits into a code
Signaling: the method of representing bits
Physical components: hardware and connectors

Question 2

Bit time

Answer 2

Each signal has a certain time to occupy media

Question 3

NRZ

Answer 3

Signaling method suitable for slow speed data links

Question 4

Code groups

Answer 4

A set of encoded symbols to represent encoded data or control info

Question 5

Three symbols of code groups

Answer 5

Data symbol
Control symbols: controls transmission
Invalid symbol: not allowed on media

Question 6

Frequent transitions

Answer 6

Less individual bit errors and less sync loss

Question 7

Balancing 1s and 0s

Answer 7

DC balancing

Question 8

Data transfer measured in three ways:

Answer 8

Bandwidth: amount of info flowing from one place to another
Throughput: measure of transfer of bits across media over time
Goodput: transfer of useable data

Question 9

Crosstalk

Answer 9

Interference in the twisted pairs of wires via their magnetic field

Question 10

Copper cable

Answer 10

Connects LAN devices to intermediate devices such as routers and switches

Question 11

Coaxial cable

Answer 11

Consists of a copper conductor surrounded by a layer of flexible insulation

Question 12

Uses of coaxial

Answer 12

Wireless and cable technologies; most widely used for transporting high radio frequency signals over wire

Question 13

Fiber optic characteristics

Answer 13

Immune to electromagnetic interference; relatively low signal loss; operated at greater lengths than copper; uses glass or plastic fibers to guide light impulses from source to destination

Question 14

Single mode optical fiber

Answer 14

Single ray of light emitted usually from a laser; can transmit optical pulses for very long distances; uses subscriber connector

Question 15

Multimode fiber

Answer 15

Cheaper than single mode; uses Lucent and straight tip connectors; uses led to generate light pulses on the media.

Question 16

Wireless characteristics

Answer 16

Carry electromagnetic signals at radio and microwave frequencies; performs well in open environments; interference from cordless phones, microwaves, other wireless devices

Question 17

Wireless networks

Answer 17

802.11 wifi
802.15 wpan Bluetooth
802.16 WiMAX point to multi point topology worldwide interoperability for microwave access
Gsm

Question 18

Wireless LAN requires

Answer 18

Wireless access point

Wireless NIC adapters

Question 19

Wireless standards

Answer 19

802. 11a 5 ghz 54 Mbps, not interoperable with 802.11b, 802.11g
803. 11b 2.4 ghz 11 Mbps have longer range and can penetrate buildings better
804. 11g 2.4 ghz 54 Mbps
805. 11n 2.4 ghz or 5 ghz 100-200 Mbps 70 m

Question 20

Fiber optic termination and splicing errors

Answer 20

Misalignment: not precisely aligned to one another
End gap: the media do not completely touch at the splice or connection
End finish: not well polished or dirt is present at termination

Question 21

Optical time domain reflectometer

Answer 21

Used to test each fiber optic cable segment

Question 22

Deliver of frames require

Answer 22

Physical media and associated connectors
A representation of bits in media
Encoding of data and control info
Transmitter and receiver circuitry on the network devices